Artificial ligaments for replacing biological articular ligaments, and notably those of the knee, are in certain specific cases preferred to direct suture for reconstruction by autogenously grafting. Indeed, the quality of these ligaments both on the mechanical level and on that of biocompatibility has considerably improved over the last twenty years.
Thus, for example, a prosthetic ligament in polyethylene terephtalate (PET) said to be with <<orientated fibres>> is known from French Patent FR-96 14263. This ligament consists of a cloth rolled or folded over itself, which cloth includes two extreme intra-bone portions and an intermediate intra-joint portion formed by a hank of longitudinal adjacent active weft yarns not bound to each other transversally. Upon mounting the ligament, a longitudinal twist is given to each active yarn, resulting in a dextrogyral or levogyral ligament reproducing the natural kinking of the ligaments in flexion. This type of ligament in PET, a material whose biocompatibility is well known, has an extremely high resistance to tensile, flexural and torsional stresses, leaving the presumption of a larger life expectancy than that of the known ligaments.
However, in spite of these considerable advances on the biomechanical level, failures of these artificial ligaments are still reported in patients. Investigations carried out on the causes of these failures, have demonstrated poor regrowth of fibroblasts after implantation. Indeed, the distribution of these cells is inhomogeneous at the surface of the ligament, fibroblasts not growing in the intra-bone prosthetic areas and clustering on the fibres of the intra-joint area. Further, these fibroblasts have an abnormal rounded morphology, with very little anchoring points at the surface of the ligament. Secretion of collagen by these cells is in fact erratic and causes individualization of the fibres of the intra-joint area with accumulation of fibrous tissues between the envelope and the central portion of the prostheses, thereby contributing to their failure.
Confronted with this problem of providing good fibroblastic rehabitation of prostheses, French Patent FR 2 651 994 proposes impregnation of the prosthetic ligament with collagen, collagen fibres being orientated along the longitudinal axis of the ligament in order to obtain a proper direction for its rehabitation by a living conjunctive tissue. In addition to limited and not very satisfactory efficiency, this solution has the major drawback of depending on the quality of the collagen used which is difficult to reproduce.